run Forkchoice::onBlock async in block importer

[tbenr]

When importing a block, we end up having the state transition running synchronously due to how Forkchoice::onBlock is written. In this way we run it using an async runner, which then enables a true async block import which have downstream effect on block publishing:

block publishing now starts just after the EQUIVOCATION check, without synchronously waiting the state transition

2024-11-05 18:41:13.224	
Slow Block Publishing *** Slot: 2910506 start 887ms, block_publishing_initiated +3ms, blob_sidecars_publishing_initiated +21ms, blob_sidecars_imported +7ms, block_import_completed +283ms, complete +1ms total: 315ms

for reference this is the old flow:

2024-11-05 18:42:37.393	
Slow Block Publishing *** Slot: 2910513 start 853ms, blob_sidecars_imported +26ms, block_publishing_initiated +291ms, blob_sidecars_publishing_initiated +0ms, block_import_completed +44ms, complete +0ms total: 361ms

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

[mehdi-aouadi]

LGTM